In television programming, video switchers receive video input signals from various video sources and direct (or "switch") to the switcher outputs for transmission (or recording) picture images from selected sources. The video sources can include network feeds, satellite feeds, cameras, receivers and recorders. Switching can be done manually by an operator or automatically by programming the switcher to perform a plurality of operations (or "transitions") in an predetermined sequence. Transitions can include cuts, fades, mixes and combinations thereof.
A conventional video switcher typically includes a switching unit, mix/effects (M/E) amplifiers, a control processor and a control panel. An operator manipulates various knobs, levers, and switches on the control panel. The control processor controls the switching unit and M/E amplifiers to provide the video output signal. The switching unit receives video input signals and provides the input signals to the M/E amplifiers. The M/E amplifiers, responsive to control signals from the control processor, combine selected input signals to produce a video output signal. For convention switchers capable of supporting live broadcasts, the control processor is synchronized to the video frame rate and provides real time switching functionality within 1/60th of a second.
Over the years, video switchers have utilized various types of technology. Known analog video switchers have used analog circuitry and a single processor running a proprietary closed architecture operating system. Known digital switchers have used one or more processors running a proprietary closed architecture operating system. For example, the Grass Valley Group manufactures a digital production switcher (Model 2200.TM.) having multiple processors running a proprietary closed architecture operating system. These closed architecture switchers are essentially fixed in their capabilities when manufactured and are generally not upgradeable by third parties.
In recent years, video switcher companies have attempted to take advantage of the increased capability of standard platform computing systems (i.e., PC-based open architecture systems). By way of example, Pinnacle manufactures a digital switcher (Alladin.TM.) that operates in conjunction with a personal computer (PC). The switcher couples to the PC through a SCSI port. The switcher includes a control processor running a proprietary closed architecture operating system, and the PC includes a general purpose processor running an open architecture operating system. The control processor provides real time switching for live broadcasting. The PC processor provides non-real time switching (e.g., off-line image processing and image storage), but is incapable of providing real time switching functionality. In another example, Matrox manufactures a digital switcher (DigiMix.TM.) that includes standard platform computing capability. More specifically, the switcher includes a control processor and a general purpose processor. However, the two processors are not independent of each other, and the general purpose processor is not synchronized to the video frame rate. Thus, the switcher is incapable of providing real time switching functionality.
The assignee of the subject application, ECHOlab, Inc., manufactures two switching products that include standard platform computing capability. ECHOlab's PC-A is a two-channel audio switcher on a standard IBM circuit card that can be plugged into a PC. ECHOlab's PC-3 is a video switcher on a standard IBM circuit card capable of being plugged into a PC. Both products can be controlled by an on-board control processor or a general purpose processor running the Windows.TM. NT operating system on the PC. After installation of either product in the PC, the two processors are independent of each other and tightly coupled.
The PC-3 is incapable of providing real time switching functionality in live broadcast environment for at least two reasons. First, the general purpose processor is not synchronized to the video frame rate. Second, Windows.TM. application software running on the general purpose processor provides the control panel as a window on the PC display. Thus, the control panel would not survive a PC failure in a broadcast environment.